books.google.ca - The U-boats constituted a serious threat to North American security and a major challenge to coastal and convoy defence. Hadley reveals the military and political impact on Canada of in-shore submarine warfare and vibrantly documents the successful German strategy of deploying daring long-range solo...http://books.google.ca/books/about/U_Boats_Against_Canada.html?id=LJJez91DyYcC&utm_source=gb-gplus-shareU-Boats Against Canada